1. Field of the Invention
This invention relates to a laser diode pumped solid laser. This invention particularly relates to a laser diode pumped solid laser having an improved structure for the adjustment of the temperature of an optical module.
2. Description of the Prior Art
Laser diode pumped solid lasers have been proposed in, for example, U.S. Patent Nos. 4,656,635. The proposed laser diode pumped solid lasers comprise a solid laser medium, to which a rare earth metal, such as neodymium (Nd), has been added. The solid laser medium is pumped by a semiconductor laser (a laser diode). In the laser diode pumped solid laser of this type, in order for a laser beam having as short a wavelength as possible to be obtained, a crystal of a nonlinear optical material for converting the wavelength of a solid laser beam, which has been obtained from solid laser oscillation, is located in a resonator of the solid laser. The solid laser beam is thereby converted into its second harmonic, or the like.
In cases where such a laser diode pumped solid laser is used, the temperature of an optical module, which comprises a laser diode, a solid laser crystal, and a resonator, is ordinarily adjusted at a predetermined temperature such that the output power of the laser diode, which serves as a pumping source, and the wavelength of the laser beam, which is produced by the laser diode, can be prevented from fluctuating. In cases where the crystal of a nonlinear optical material for converting the wavelength of the produced solid laser beam is located in the resonator, the temperature of the optical module is ordinarily adjusted at a predetermined temperature such that a predetermined phase matching state can be kept in the nonlinear optical crystal. The adjustment of the temperature is ordinarily carried out by placing the optical module on a cooling surface of an electronic cooling device (or a Peltier device), detecting the temperature at a position in the vicinity of the laser diode or the nonlinear optical crystal, and controlling the electronic cooling device in accordance with the detected temperature.
In the laser diode pumped solid laser described above, as in the other various laser apparatuses, for the purposes of protection of the optical module and heat insulation from the exterior, the optical module is housed in a single case housing, and a laser beam is taken out through a beam take-out window, which is formed in a wall of the case housing. The case housing has heretofore been constructed such that the optical module and the electronic cooling device may together be housed in the case housing, and such that a heat radiating surface of the electronic cooling device may be supported by the case housing.
However, with the conventional laser diode pumped solid laser, in which both the optical module and the electronic cooling device are housed in a single case housing, the accuracy, with which the temperature is adjusted, cannot be kept sufficiently high, and the temperature in the region inside of the case housing is apt to fluctuate. If the temperature in the region inside of the case housing fluctuates, the output power of the laser diode, which serves as the pumping source, and the wavelength of the laser beam, which is produced by the laser diode, will fluctuate. As a result, the output power and the wavelength of the solid laser beam, which is obtained from solid laser oscillation, will fluctuate.
Also, if the temperature in the region inside of the case housing fluctuates, the optical parts housed in the case housing will move due to thermal expansion and contraction, or the temperature of the nonlinear optical crystal, which is employed in order to convert the wavelength of the produced solid laser beam, will fluctuate. As a result, the predetermined phase matching state cannot be obtained. In such cases, the output power of the beam will fluctuate, and the quality of the beam will become bad.